The Oregonian reported that two bikers with critical injuries were flown to Portland hospitals by helicopter. The newspaper said the incident, which involved 26 bikers, backed up traffic for about 7 miles.

Rescue personnel said seven other people were treated for shoulder and hip injuries and broken bones.

Most of the victims belonged to the Brother Speed motorcycle club, officials said. The Oregonian reported that the group is identified by the state's Department of Justice as an outlaw biker gang.

The freeway reopened about 6 p.m., nearly four hours after the accident.